Distortion in the phase currents of an electric motor can contribute to motor torque ripple, which leads to rough actuator motion, especially at low speeds. This effect is observable in surgical robot arms that have multiple joints (each joint being actuated by one or more electric motors that may be running simultaneously), particularly when a user moves the arm by hand. The user feels the irregular actuation of the joints. Also, higher layer robot control algorithms that rely on operating a joint in torque mode (using the sensed phase current as feedback to compute a motor torque input command) are adversely impacted by the torque ripple. There is therefore a need for a calibration procedure that enables more accurate sensing of motor phase current which enables smoother control of a surgical robotic arm joint, by reducing the motor torque ripple. In addition, a power on self-test procedure is needed that verifies the integrity of the phase current sensing process.